1. Field of the Invention
The present invention relates generally to upwardly-acting door structures which are adapted to selectively cover or uncover an access opening provided through a body member.
2. Description of the Prior Art
Theft, damage and pilferage during transport are problems which have plagued the automobile and transportation industries. These problems are believed to be particularly acute when automobile-carrying railroad cars are left unattended on unsupervised sidings for considerable lengths of time.
One proposed solution to this problem is to completely enclose the railroad car so as to deny access to thiefs and vandals. However, access and communication between adjacent cars must be provided, when needed, so that automobiles may be driven through adjoining railroad cars during an on-loading or off-loading operation.
Inasmuch as these railroad cars commonly have three levels or tiers on which automobiles or other cargo may be stored, it is believed desirable to expose all such tiers or levels simultaneously during a loading operation.
One proposed door in the prior art included three panels, all of which could be adjustably positioned at one of the levels to expose the two other levels. However, after one level had been loaded or unloaded, each of the doors had to be readjusted to expose another level. Hence, the three levels were not simultaneously exposed.
The problem of designing an adequate door for this environment has been further complicated by the fact that a laterally-movable door might possibly interfere with passing trains.